This proposal is concerned with the study of the role of sleep posture in sleep apnea syndromes. Major goals include: 1) establishing the importance of posture monitoring to reliable diagnosis and 2) demonstrating the utility of posture correction in the treatment of sleep apnea. Patients will be monitored for respiration and sleep posture in sleep laboratories at four performance sites using standard polysomnographic techniques. Patients with a positional effect in their sleep apnea will wear a monitor/alarm device to prevent back sleeping. Effectiveness of this treatment will be determined by additional laboratory and home monitoring evaluations. Evaluation of the equipment at multiple performance sites will provide data required for support of an application for FDA Premarket Approval. Furthermore, successful testing at prestigious treatment centers such as those selected will provide convincing evidence to the community of sleep disorder clinicians of the efficacy and utility of the Sleep Posture Monitor and Alarm System in the diagnosis and treatment of sleep apnea syndromes. It is anticipated that posture monitoring and sleep posture correction will become standard procedures in the diagnosis and treatment of sleep apnea, thus removing a current source of diagnostic error and obviating the application of potentially hazardous treatments where not necessary.